Re: sysctl, ip_forward[ing], Configure.help
Andreas Kleen (ak@muc.de)
Thu, 8 Jan 1998 06:16:43 +0100
>
> On 5 Jan 1998, Andi Kleen wrote:
>
> > alan@lxorguk.ukuu.org.uk (Alan Cox) writes:
> >
> > > > fact was documented somewhere, e.g. by adding a sentence like
> > > > You have to enable IP forwarding by doing
> > > > echo "1" > /proc/sys/net/ipv4/ip_forward
> > > > (cc to Axel, just in case there will be a 2.0.34;
> > >
> > > This isnt correct. In 2.0.x you have to set forwarding at compile time
> > > unless using some vendors magically tuned krnel
> >
> > Someone incorporated my old ip_forward sysctl patch into 2.0.30 (it
> > wasn't me, I'm not to blame). The compile time option selects only the
> > default too, so if the kernel is compiled with IP_FORWARD it'll do the
> > right thing at runtime. Setting of the sysctl is only needed when
> > CONFIG_IP_FORWARD isn't enabled.
> >
> > If the documentation Andries is refering too doesn't specify that the
> > kernel needs to be compiled with CONFIG_IP_FORWARD it was all always
> > wrong.
>
>
> The howto did mention a compile time requirement of enabling ip
> forwarding. In fact, I'm running 2.0.33 with ip forwarding compiled into
> the kernel, and it works without explicitly changing the status of
> ip_forward. So I guess this only affects users who have not compiled the
> kernel with ip_forward enabled.
>
> However, one user does report that the IP Forwarding option during make
> config (2.1.78 source) is missing, he has to run
> echo "1" > /proc/sys/net/ipv4/ip_forwarding
> to make it work. I have not been following the development kernel, so I
> can't verify.
This is correct, we got rid of CONFIG_IP_FORWARD there. The sysctl is the
correct way to set it now. My statement was only about 2.0.x (and the HOWTO
too).
-Andi